1. Field of Invention
The present invention relates to a capacitor, and more particularly, to a common centroid symmetric structure capacitor.
2. Related Art
Currently, the development of the SOC technology becomes increasingly matured and the integration of IC circuits is complicated, such that the quantity of the components accommodated in a unit area must be increased correspondingly. Therefore, many passive components that must be externally connected due to a large area thereof, such as capacitors and inductors, must be integrated into one chip.
In an IC layout, a plate capacitor is formed by different metal layers. By using a vertical electric field, with the reduction of effective line width, the occupied chip area is increased correspondingly. Furthermore, under the circumstance that the line width is reduced, with a limited area or volume, how to achieve the same capacitance is also a major technical problem of the IC layout. Thus, prior arts have provided many solutions.
For example, U.S. Pat. No. 5,208,725 discloses a capacitor structure having a first conductive layer and a second conductive layer. Each of the conductive layers comprises a plurality of stripe structures which are parallel to each other. The main technical features are that a finger structure is adopted and a lateral electric field and a vertical electric field are utilized to enhance the capacitance density.
U.S. Pat. No. 6,037,621 discloses a capacitor structure having a lower metal layer and an upper metal layer. An array of metal islands disposed between the lower and the upper metal layers, and each island of the array of islands is connected to either the upper layer or the lower layer. The main technical features are that the array of metal islands is realized through vias formed between the metals and a lateral electric field and a vertical electric field are utilized to enhance the capacitance density.
U.S. Pat. No. 6,297,524 discloses a capacitor structure having a first conductive layer and at least one second conductive layer. The conductive layers are formed of electrically conductive concentric ring-shaped lines which are arranged in concentric ring-shaped stacks. Each of the conductive layers is connected by a conductive via. The main technical features of the patent are that a concentric ring-shaped structure is utilized, a lateral electric field is utilized, and the upper and lower metals are penetrated by a via, so as to enhance the capacitance density.
U.S. Pat. No. 6,410,954 discloses a capacitor structure consisting of a first conductive layer and at least one second conductive layer. The conductive layers are formed of open-loop concentric ring-shaped lines and the second conductive layer covers the first conductive layer. The main technical features of the patent are that a ring-shaped structure is also utilized, and a lateral electric field and a vertical electric field are utilized by interlacing an upper metal and a lower metal, so as to enhance the capacitance density.
U.S. Early Publication No. 2004/0036143 discloses a capacitor structure, in which an inner vertical plate and an outer vertical plate are disposed on a substrate, a grid structure is defined by the outer vertical plate, and meanwhile a horizontal plate is disposed, so as to prevent parasitic capacitance from being generated between the substrate and the inner and outer vertical plates. The main technical features are that a grid structure is employed and a lateral electric field is utilized to enhance the capacitance density.
U.S. Pat. No. 6,737,698 discloses a capacitor structure, and the main technical features are that a mask structure is utilized to limit an electric field between two masks.
U.S. Pat. No. 6,765,778 discloses a capacitor structure consisting of a plurality of stacks. A second stack is a first nearest neighbor to a first stack, a third stack is a second nearest neighbor to the first stack, and each of the three stacks defines vertices of an isosceles triangle formed in a plane substantially perpendicular to the three stacks. The main technical features are that a hexagonal perpendicular stacking structure and a lateral electric field are utilized to enhance the capacitance density.
U.S. Early Publication No. 2004/0174655 discloses a capacitor structure mainly consisting of two layers of finger structures interlaced with each other. The main technical features are that the finger structures are utilized, and the finger structures on the upper and lower layers are perpendicularly interlaced, so as to reduce the unmatched conditions of the interlayer metals and enhance the capacitance density.
U.S. Early Publication No. 2005/0280060 discloses a capacitor structure, in which an inner box-shaped capacitor and an outer box-shaped capacitor are arranged in a concentric nested shape. The main technical features are that a concentric ring-shaped structure is utilized and a lateral electric field is utilized to enhance the capacitance density.